A pressure proportional control valve is known as a related invention to the present invention. This pressure proportional control valve has a constitution as shown in FIG. 5 (for example, refer to Patent document 1). This pressure proportional control valve is a 3 way valve for pressure control of switching clutch provided at a line of a control system at the automatic transmission, for pressure control of a switching brake, and for pressure control of the line.
Here, this preceding pressure proportional control valve will be explained in detail. In FIG. 5, the pressure proportional control valve 100 is constituted from a valve main body 101 and a solenoid 150. A communication chamber 103 is formed at the inside of a main body 102 forming an outer frame of the valve main body 101. In this communication chamber 103, an inflow port 105 communicating with the outside, an outflow port 106 and an outlet port 107 are formed. Furthermore, the communication chamber 103 is divided into a first communication chamber 103A communicating with the inflow port 105 via the partition plate 110, and a second communication chamber 103B communicating with the outflow port 106. At the center of the partition plate 110, a first valve hole surrounding surface 110A is formed. At the side of the first communication chamber 103A of this first valve hole surrounding surface 110A, a first valve seating surface 110B is formed. Also, at the side of the second communication chamber 103B of the first valve hole surrounding surface 110A, a plurality of passage grooves 110C, which does not penetrate towards the axis direction along the surrounding surface, is formed. When a first valve surface 120A of the first valve body 120 opens by separating from the first valve seat surface 110B, this passage groove 110C becomes a flow passage wherein the working fluid flows by working together with an indented portion at the middle of the first valve body 120.
Also, at the main body 102, a first pressure chamber 108 is formed between the first communication chamber 103A and the outlet port 107. At the surrounding surface of this first pressure chamber 108, a first sliding surrounding surface 108A is formed. At the first sliding surrounding surface 108A, a first annular groove which mounts a first seal ring S1 is provided. Furthermore, at the main body 102, a second pressure chamber 109 communicating with the second communication chamber 103B is formed. At the surrounding surface of this second pressure chamber 109, a second sliding surrounding surface 109A is formed. At the second sliding surrounding surface 109A, a second annular groove which mounts a second seal ring S2 is provided.
Also, the first valve body 120 is provided in which an outer circumference surface 120C fits movably to the first sliding surrounding surface 108A of the main body 102 and the first valve hole surrounding surface 110A of the partition plate 110. An axis of this first valve body 120 is provided with a communication passage 120D which communicates with the first pressure chamber 108 and the second pressure chamber 109. Also, this first valve body 120 is pressed resiliently towards a second valve body 125 side by a first spring 140A arranged at the first pressure chamber 108. Furthermore, the first valve body 120 is provided with the first valve surface 120A at the middle portion, and the second valve surface 120B is provided at the edge portion. Also, a second spring 140B is arranged between the first valve body 120 and the second valve body 125; and due to the second spring 140B, the first valve body 120 and the second valve body 125 is pressed resiliently to the opposite direction.
Furthermore, the second valve body 125 which fits movably to the second sliding surrounding surface 109A of the main body 109 is arranged. The second valve body 125 is formed in a cylindrical form, and comprises a second valve seat surface 125A having a taper surface at the inner circumference surface of one end portion. Also, one end of the solenoid rod 151 is connected to the fitting hole provided with a plurality of passage 125C along the circumference surface of other end portion of the second valve body 125. The both end sides of the solenoid rod 151 is guided so that it can freely slide due to the first bearing 154A and the second bearing 154B. Furthermore, the second valve seat surface 125A of the second valve body 125 is opened and closed with the second valve surface 120B by operating the solenoid rod 151 in accordance with the scale of the electrical current flowing to the solenoid 150.
In the operation of the pressure proportional control valve 100 constituted as such, the first valve surface 120A of the first valve body 120 is closed by contacting to the first valve seat surface 110B due to the elasticity of the first spring 140A. Further, the working fluid flowing from the inflow port 105 is blocked by closing this first valve surface 120A. Also, when the solenoid 150 operates, the second valve surface 120B of the first valve body 120 and the second valve seat surface 125A of the second valve body 125 are closed by contacting to each other, and the first valve surface 120A of the first valve body 120 are opened by separating from the first valve seat surface 110B. Due to this opening of the first valve surface 120A, the working fluid flowing from the inflow port 105 flows out to the second communication chamber 103B side. Note that, in the open-close valve state shown in FIG. 5, the first valve body 120 and the second valve body 125 are opened. Hence, the working fluid will flow out from the outflow port 106 to the outlet port 107.
Further, in the pressure proportional control valve 100, the first valve body 120 open and close while the outer circumference surface 120C and the first sliding surrounding surface 108A slides against each other, and at the same time the first seal ring S1 and the outer circumference surface 120C slides with strong friction. Thus, the sliding resistance of the first valve body 120 becomes large during the opening and closing of the valve. Particularly, when the pressure of the working fluid is high, due to this pressure, the first seal ring S1 deforms resiliently by stretched towards the radial direction; hence the first seal ring S1 slides while abrading strongly against the first valve body 120 which contacts closely. Therefore, the sliding resistance of the first valve body 120 becomes large, thus the response performance of opening and closing of the pressure proportional control valve declines.
Also, the outer circumference surface 120C of the first valve body 120 slides together with the first sliding surrounding surface 108A. The working fluid flows in between this sliding surfaces, hence the impurities included in the working fluid may be present therebetween. Thus it causes a delay in the response time of the operation of the first valve body 120 pressed by the first spring 140A in which the force is changed depending on the position which deviates. Furthermore, this first valve body 120 may be pressed against one side of the surface inside the surrounding surface and cause a sticking phenomena (known as hydro lock) at between the sliding surface. As a result, the working characteristic of the pressure proportional control valve 100 changes which causes to enlarge the hysteresis phenomena between the relation of the working fluid pressure and the fluid flow. Further, the constitution which slides the first valve body 120 simultaneously with the two separate axis of the first sliding surrounding surface 108A and the first valve hole surrounding surface 110A requires precise manufacturing thus the cost for assembling and manufacturing raises.
The diameter of the second valve body 125 is formed larger than that of the first valve body 120, hence the force affecting the pressure receiving area of the second valve body 125 becomes large along with the pressure of the working fluid becoming high. If this force becomes large, the output force of the solenoid 150 must become larger which works against this force. Therefore, the solenoid 150 becomes large, and the cost for the solenoid 150 also increases. Also, the sliding resistance during the operation of the second valve body 125 becomes large due to the friction of the second seal ring S2 provided between the outer circumference surface of the second valve body 125 and the second sliding surrounding surface 109A of the main body 102. Furthermore, along with the increase of the pressure of the working fluid, the second seal ring S2 also deforms resiliently such that it is stretched in the radial direction, thus the sliding resistance of the second valve body further increases. Therefore, there is a problem that the solenoid 150 had to be even larger.
Patent document 1: Japanese Patent Laid Open 2004-197858